Gastrointestinal motility and disease in large animals

Spasmolytic effect of 1,8 cineole is mediated through calcium channel blockade in the bovine ileum

Gastrointestinal motility disorders include increased or decreased movements. Other studies have shown that herbal components, for example, essential oils can modify the increase and decrease of gastrointestinal movements of ruminants. The 1,8-cineole being obtained from the essential oil of many plants has several effects. The present study has investigated the effect of 1,8-cineole on the contractility of bovine ileum smooth muscle. The experiment was performed on the circular smooth muscle of ileum samples taken from slaughtered cows in the organ bath. Seven cumulative concentrations of 1,8-cineole from 1.00 to 1,000 µg mL^-1 were added to tissue samples. The used solution was Tyrode's solution aerated with a mixture of 95.00% oxygen and 5.00% carbon dioxide, and the temperature was set at 37.00 ˚C. The effects of 1,8-cineole on baseline contractions and three induced contractions with barium chloride, potassium chloride, and carbachol were investigated. The effects of 1,8-cineole, and verapamil (standard calcium channel blocker) on calcium channels were assessed. The results revealed that 1,8-cineole significantly inhibited spontaneous contractions as well as all spasmogen-induced contractions. The 1,8-cineole exerts its myorelaxant properties by inhibiting calcium channels in smooth muscle. It seems that 1,8-cineole has a good potential for producing antispasmodics or gastrointestinal motility modulators in veterinary medicine.

The effect of cinnamaldehyde on the contractility of bovine isolated gastrointestinal smooth muscle preparations

Gastrointestinal motility disorders can occur as either increased or decreased movements. Studies have shown that herbal ingredients such as essential oils can modify the increase and decrease of gastrointestinal movements of ruminants. Cinnamaldehyde at room temperature is an oily yellow liquid which is obtained from the steam distillation of the oil of cinnamon bark. It bears carminative activity and gastrointestinal, antimicrobial, and vasodilatory effects. This study examined the effects of cinnamaldehyde on the contraction of circular smooth muscles of abomasal fundus and the antrum, duodenum, and ileum of healthy cows using an in vitro approach. The results indicated that cinnamaldehyde had relaxant effects on the basal tonus and contractions caused by barium chloride (BaCl₂) and carbachol (CCh) in these tissues dependent upon concentration and the origin of the smooth muscle. These effects were more prominent in the ileal smooth muscle preparations than in other tissues. This substance in the smooth muscle preparations of the abomasal fundus not only had no significant effect on the basal tonus, but also significantly increased the contractions caused by barium chloride at low concentrations. Study of the mechanism of action showed that, similar to verapamil, cinnamaldehyde applied its relaxation effect by blocking the calcium channels. The results showed that cinnamaldehyde possessed a spasmolytic effect mediated through blockage of the calcium channels, which may provide a pharmacological base to its medicinal use for diarrhea and spasms.

Obstrução intestinal em bovinos associada ao consumo de Stylosanthes sp. (Fabaceae Papilionoideae)

O objetivo deste trabalho é descrever, em três propriedades rurais no Estado de Mato Grosso, a epidemiologia, o quadro clínico e o patológico da obstrução intestinal por fitobezoares em bovinos que pastoreavam em piquetes com predomínio de Stylosanthes sp. pelo menos 60 dias. A morbidade variou de 3,3% a 15% e a mortalidade foi de 100%. O quadro clínico foi de cólica abdominal caracterizado por apatia, anorexia, inquietação, desconforto, sudorese e vocalização, seguido por episódios de diarreia ou diminuição da produção fecal, desidratação, hipomotilidade gastrintestinal, aumento do volume abdominal, decúbito esternal ou lateral com a cabeça voltada para o flanco e morte. O curso clínico foi de 2-7 dias. A principal alteração notada durante a necropsia dos bovinos foi a obstrução intestinal por fitobezoar ovoide de 2-5 cm de diâmetro, frequentemente no duodeno, próximo ao piloro, ocasionalmente em sua porção média. Na área de obstrução notou-se a necrose da parede intestinal que estava enegrecida e intensamente demarcada em relação a segmento adjacente normal, além de intenso espessamento associado a edema, congestão e hemorragia. O abomaso e os segmentos intestinais anteriores a obstrução apresentavam-se repletos de conteúdo alimentar líquido e posteriormente estava com ausência de conteúdo. O rúmen frequentemente tinha grande quantidade de conteúdo liquido a pastoso. Em todos os bovinos necropsiados múltiplas estruturas sólidas, arredondadas ou ovoides, esverdeadas (fitobezoares) foram observadas no abomaso. Estes achados indicam que pastagens com predomínio de Stylosanthes sp. predispõem a formação de fitobezoares, os quais podem levar à obstrução intestinal e morte em bovinos.

Abomasal impaction in captive bongo (Tragelaphus eurycerus)

Fatal abomasal impaction, often combined with omasal impaction, was diagnosed in 11 bongo (Tragelaphus eurycerus) from five different zoologic collections in the United States between 1981 and 2009. Nine of 11 cases occurred in young females (10 mo-7 yr old) and typical clinical signs prior to diagnosis or death included partial or complete anorexia, dehydration, and scant fecal production. Although the clinical histories in several of the earlier cases are incomplete, clinical signs were known to begin shortly after an anesthetic event in five of 11 bongo (45%). Pedigree analysis indicates that affected bongo were descendants of multiple founders and not from a single family line, suggesting that the development of abomasal impaction is not a strictly inheritable trait. Treatment, when attempted, was variable and included abomasotomy and removal of impacted ingesta, drug therapy (prokinetic drugs, nonsteroidal anti-inflammatories, antimicrobials), fluid therapy, and administration of oral lubricants or intralesional stool softeners. Based on the outcomes in the cases presented here, the prognosis for bongo with abomasal impaction is considered poor to grave.

Effect of intraluminal distension or ischemic strangulation obstruction of the equine jejunum on jejunal motilin receptors and binding of erythromycin lactobionate

OBJECTIVE

To determine whether inflammation of the jejunum of horses decreases the number of motilin receptors and amounts of motilin receptor mRNA and alters erythromycin lactobionate binding affinity to the motilin receptor in jejunal tissues.

SAMPLE POPULATION

Jejunal segments in 6 adult horses.

PROCEDURE

Each horse was anesthetized, and a ventral median celiotomy was performed; 2 segments of jejunum underwent a sham operation, 2 segments underwent ischemic strangulation obstruction (ISO), and 2 segments underwent intraluminal distension (ILD). Treatments were maintained for 120 minutes. From each segment, full-thickness biopsy samples were collected and smooth-muscle homogenates were prepared. Affinity and distribution of motilin binding to these preparations were determined by use of iodine 125 (125I)-labeled synthetic porcine motilin. Via displacement experiments, competition between 125I-labeled motilin and erythromycin lactobionate for binding to motilin receptors in the different segments was investigated. A quantitative real-time PCR technique was used to assess motilin receptor mRNA content in the muscle preparations.

RESULTS

Compared with the ISO or ILD segments, the number of motilin receptors was significantly higher in the sham-operated segments; ILD segments contained the lowest number of motilin receptors. The expression of motilin receptor mRNA was significantly decreased in ILD segments but not in ISO segments. Erythromycin lactobionate displacement of 125I-labeled motilin from motilin receptors did not differ significantly among the jejunal segments.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that downregulation and decreased production of motilin receptors in inflamed jejunal tissue contribute to the altered prokinetic response to erythromycin in horses with gastrointestinal disease.

Equine gastrointestinal motility--ileus and pharmacological modification

Colic is a common problem encountered in equine practice. Alteration of gastrointestinal motility is often the underlying cause for abdominal pain. Gastrointestinal motility can be measured as myoelectric activity, mechanical activity, and transit of intraluminal contents. Regulation of motility is based on a complex interaction between central innervation, autonomic innervation, and the enteric nervous system. Various humoral and neurochemical substances are required to interact flawlessly to allow propulsive motility. Ileus is defined as the absence of propulsive aboral movement of gastrointestinal contents, irrespective of its pathophysiology. Potential etiologies for ileus are described in this review. The prokinetic drugs available for clinical use are discussed. Choosing the appropriate prokinetic drug requires knowledge about the complex nature of gastrointestinal motility and its abnormalities.

Effect of Escherichia coli Heat-labile Enterotoxin on the Myoelectric Activity of the Duodenum in Weaned Pigs

The objective of the present study was to elucidate the effect of subclinical doses of Escherichia coli heat-labile enterotoxin (LT) on the antro-duodenal myoelectric activities of weaned pigs. Twelve weaned pigs were surgically implanted with three pairs of electrodes on the antrum 3 cm before the pylorus, 5 and 20 cm after the pylorus on the duodenum, respectively. An infusion cannula was inserted into the duodenum between duodenal electrodes. Using a wireless telemetry recording system, an electromyography (EMG) tracing lasting at least 24 h was recorded as the control, then another 24-h EMG recording was performed with a bolus intraduodenal infusion of LT (0.1 and 0.5 microg/kg b.w.). After a 1- to 2-day break, a 5-fold higher dose of LT was administered using the same protocol. In the antrum, LT administration barely modified the EMG signal. However, in the duodenum it prolonged the duration of phase II and the migrating myoelectric complex (MMC) cycle when compared with the control. The number of duodenal MMC cycles was also significantly diminished. Moreover, the migrating velocity of phase III was increased. The migrating action potential complex (MAPC) was present both without and with LT, but occurred more frequently following LT administration. In conclusion, LT caused a dose-dependent, lagged alteration in the duodenal MMC in weaned pigs, involving a reduction of the MMC number by lengthening phase II, increased phase III migration velocity, and increased MAPC frequency. The disturbances did not, however, result in diarrhoea and may reflect the induction of a local protection mechanism of the gut to expel unwanted foreign content from the lumen of the upper gut.

Presence of in vitro electrical activity in the ileum of horses with enteric nervous system pathology: equine dysautonomia (grass sickness)

Equine dysautonomia (grass sickness) is a frequently fatal disease of horses characterised by intestinal stasis. Interstitial cells of Cajal (ICC) are the pacemakers and mediators of neurotransmission in the gastrointestinal tract. Impaired ICC-mediated control of motility has been implicated in intestinal disorders in laboratory mammals, humans and in equine grass sickness. The aim of this study was to compare the in vitro electrical properties of ileum from grass sickness cases with horses free from gastrointestinal disease. Intracellular microelectrode recordings were made from smooth muscle cells in cross-sectional preparations of equine ileum, superfused in vitro. Samples were taken from six horses with grass sickness and from eight horses free from gastrointestinal disease, all euthanised on humane grounds. Ileal tissues were processed for haematoxylin and eosin histology, and c-Kit immunohistochemistry. Membrane potential oscillations were recorded in the ileal preparations from four of the six horses with grass sickness and from all of the normal horses. A waxing and waning pattern of the membrane potential oscillation activity was noted in some cells. In comparison to the normal horses, the membrane potential oscillations in grass sickness horses had a significantly reduced frequency (P = 0.0001) and increased duration (P = 0.0002). Immunohistochemistry revealed the presence but reduction of ICC in grass sickness. Histological assessment of the same tissues used for analysis of the ICC showed the depletion and pathology of the enteric neurons in grass sickness. Therefore, the majority of ileal preparations from grass sickness-affected horses exhibited prominent membrane potential oscillation activity suggesting that, although the neural elements are damaged severely, the ICC-mediated pacemaker function remains intact.

Gastrointestinal pharmacology

Diseases of the gastrointestinal tract that require pharmacologic management, usually in combination with other treatments, are gastric ulcers (omeprazole and others), colic (laxatives, analgesics), diarrhea (antibiotics, protectants and absorbents, glucocorticoids, motility inhibitors), reperfusion injury, postoperative ileus (prokinetic drugs), and adhesions. There is growing evidence that nonsteroidal anti-inflammatory drugs can alter important physiologic properties of the intestine; however, these drugs are valuable analgesics for horses and their use should be tempered with an awareness of their harmful effects. The role of antibiotics in treating gastrointestinal disease is controversial, but their ability to induce life-threatening diarrhea is well known and invites caution and defensible use of these drugs in horses.

Rumen motility during induced hyper- and hypocalcaemia

Rumen motility was recorded on an experimental cow by means of telemetric signal transfer from strain gauge force transducers fixed surgically on the peritoneal surface of the rumen wall in the left flank. The normocalcaemic cow was given a standard milk fever treatment with calcium borogluconate (400 ml with 14 mg Ca/ml) intravenously. Transient clinical signs were: decreased rumination, muscle ticks, salivation and a heart rate reduction of 20%. Rectal temperature remained unaltered. Frequency of rumen contractions was reduced up to 40% whereas amplitude of contractions did not deviate from baseline values. Hypocalcaemia was induced in a second experiment by iv infusion of Na2EDTA. At 0.60 mmol/l ionized blood calcium periods of no motility were recorded whereas inactivity of rumen activity was persistent at 0.55 mmol/l ionized blood calcium. The cow went down at 0.45-0.48 mmol/l ionized blood calcium at which point the heart rate was increased by 40%. The high sensitivity of the method employed allowed the conclusion that already at a concentration of ionized blood calcium at 1.0 mmol/l both frequency and amplitude of rumen contractions decreased rapidly although eating behaviour and rumination appeared unaffected during the short term observation periods. Implications of this finding towards health and production in transition cows are discussed.

Rumen motility during induced hyper- and hypocalcaemia

Rumen motility was recorded on an experimental cow by means of telemetric signal transfer from strain gauge force transducers fixed surgically on the peritoneal surface of the rumen wall in the left flank. The normocalcaemic cow was given a standard milk fever treatment with calcium borogluconate (400 ml with 14 mg Ca/ml) intravenously. Transient clinical signs were: decreased rumination, muscle ticks, salivation and a heart rate reduction of 20%. Rectal temperature remained unaltered. Frequency of rumen contractions was reduced up to 40% whereas amplitude of contractions did not deviate from baseline values. Hypocalcaemia was induced in a second experiment by iv infusion of Na2EDTA. At 0.60 mmol/l ionized blood calcium periods of no motility were recorded whereas inactivity of rumen activity was persistent at 0.55 mmol/l ionized blood calcium. The cow went down at 0.45-0.48 mmol/l ionized blood calcium at which point the heart rate was increased by 40%. The high sensitivity of the method employed allowed the conclusion that already at a concentration of ionized blood calcium at 1.0 mmol/l both frequency and amplitude of rumen contractions decreased rapidly although eating behaviour and rumination appeared unaffected during the short term observation periods. Implications of this finding towards health and production in transition cows are discussed.

The quantitative effect of metoclopramide on abomasal and duodenal myoelectric activity of goats

Electromyographic (EMG) recordings of the abomasal corpus, pyloric antrum and proximal duodenum were made from six goats for 2 h periods before and after administration of 0.5 mg/kg metoclopramide intravenously or intramuscularly. Analog EMG signal was transformed via a computer program to digital data. The percentage change in electrical activity was determined by comparing the electrical activity following administration of IV or IM metoclopramide with the electrical activity of the control periods for the abomasal corpus, pyloric antrum and proximal duodenum. Metoclopramide caused a significant, time-dependent increase in duodenal electrical activity following either route of administration. This increase in duodenal electrical activity coincided with peak plasma levels of metoclopramide until its decline below 100 ng/ml in plasma. There was a significant biphasic increase in electrical activity of the abomasal corpus and pyloric antrum following IM administration of metoclopramide. The first phase lasted approximately 5 min and was followed by a longer period (approximately 20 min) of diminished electrical activity. A second phase of increased electrical activity occurred approximately 40-60 min after initial IM injection of metoclopramide. It is uncertain whether this increase was drug-mediated or endogenously-triggered. Similar increases in corpus and antral electrical activity were present following IV metoclopramide administration, though early increases were not statistically significant. Overall, the percentage changes in electrical activity correlated well with predicted peak plasma levels of metoclopramide only in the duodenum. This correlation was limited to approximately 5 min after IV and 15 min after IM metoclopramide administration.